The proposed research is concerned with an investigation of the synthesis of influenza virus specific mRNA and proteins. Cell-free systems are used in order to separate the viral directed biosynthetic processes and to study the requirements of the individual steps, the products formed and the role of the host cell in the syntheses. Several lines of evidence indicate that the complementary product of influenza vRNA transcription catalyzed by the virion RNA-dependent RNA polymerase is mRNA. Studies on in vitro transcription by the Ao/WSN strain of influenza virus revealed that incomplete RNA copies were formed. Current investigations in this laboratory indicate that the addition of 2 partially purified host cell factors, believed to be proteins, significantly stimulate both the rate and extent of in vitro transcription. Continuing research is directed toward further purification and identification of the host factors, an investigation of their mechanism of action and a determination of whether completed transcripts are formed in the presence of the factors. An investigation of influenza protein synthesis will employ cell- free systems programmed with viral mRNA. This study should provide information on the proteins coded by the viral RNA and the possible monocistronic nature of the genome.